1. Field
Exemplary embodiments of the present invention relate to a method of growing a nitride semiconductor layer, a nitride semiconductor device, and a method of fabricating the same, and, more particularly, to a method of growing a nitride semiconductor layer on a growth substrate prepared using a tiling technique and a nitride semiconductor device and method of fabricating the same using the nitride semiconductor layer.
2. Discussion of the Background
Nitride semiconductors such as gallium nitride semiconductors may have a wide energy band gap and may be of a direct transition type. Nitride semiconductors may be used in fabrication of semiconductor devices, such as light emitting devices having a relatively short wavelength emission range, for example, ultraviolet, blue, and green light emitting devices, electronic devices, and the like.
A nitride semiconductor layer may be grown on a heterogeneous substrate such as a sapphire substrate due to difficulty in preparation of a homogeneous substrate. However, the nitride semiconductor layer grown on the heterogeneous substrate may have a high-density of crystal defects such as thread dislocations, and thus not be suited for fabricating a device capable of being operated under high current density.
Thus, techniques for preparing a nitride semiconductor layer using a homogeneous substrate, such as a gallium nitride substrate, as a growth substrate have been developed in recent years. For example, a bulk gallium nitride single crystal may be grown on a sapphire substrate via hydride vapor phase epitaxy (HVPE) and sliced to prepare a gallium nitride growth substrate.
For mass production of semiconductor devices by growing a semiconductor layer on a substrate, it may be necessary for a growth substrate to have a relatively large size. Currently, a substrate used to fabricate optical devices such as light emitting diodes may have a size of 2 inches or more.
A c-plane gallium nitride substrate may be obtained as a large substrate having a size of about 2 inches by slicing a bulk single crystal. However, it may be difficult to form semi-polar substrates or non-polar substrates, such as m-plane or a-plane gallium nitride substrates, to a size of 2 inches or more using the above method due to a limit on a growth plane or growth thickness. For this reason, studies based on non-polar or semi-polar gallium nitride substrates are mostly limited to growth of a nitride crystal using the non-polar or semi-polar substrate having a size of less than 1 inch, for example, having a maximum width of several millimeters or less.
To provide a large-area growth substrate, a technique has been developed in which a plurality of seed substrates each having a desired crystal growth plane is arranged thereon and nitride semiconductor layers are then grown on the seed substrates, followed by slicing the grown nitride semiconductor layers.
However, due to use of the plural seed substrates, a nitride crystal grown on a boundary line between the seed substrates may include a high density of crystal defects. In addition, a gallium nitride substrate prepared using the seed substrates may show a relatively large difference in off-angle depending upon a location due to a difference in crystal orientation between the seed substrates. Even though the off-angle and arrangement of the seed substrates may be controlled, it may be difficult to completely remove off-angle distribution on the gallium nitride substrate. Thus, a portion of the nitride crystal corresponding to a boundary region between the seed substrates may act as a defect source upon growth of the nitride semiconductor layer on the gallium nitride substrate.
Moreover, a defect generated in the semiconductor layer may be transferred in a vertical direction, and also spread over a significantly wide area. As a result, it may be difficult to secure a semiconductor layer region capable of providing a semiconductor device exhibiting good properties, thereby decreasing productivity and yield.